1. Field of the Invention
The present invention relates to a motion detection imaging device.
2. Description of the Related Art
A motion detection imaging device is known which calculates a difference between images captured with a time difference on a solid-state imaging element, and detects movement or motion of a target object (to be captured or imaged) based on the calculated difference (refer to e.g. Japanese Laid-open Patent Publication 2003-32552). It is also know to detect a moving object based on a difference between digitized images (refer to e.g. Japanese Laid-open Patent Publications 2001-177836, 2004-171431 and Hei 8-106534). On the other hand, an electronic still camera is known which uses an image sensor with a light receiving surface having divided light receiving areas, and sequentially exposes images of a target object on the light receiving areas so as to allow images in the light receiving areas to be read out all together, thereby shortening the interval between shots in continuous shooting mode (refer to e.g. Japanese Laid-open Patent Publication Hei 11-352550). Furthermore, a camera is known which has four photographing lenses that are placed in front of a film so as to be fit in a frame of a film, in which a slit member is provided to pass in front of the photographing lenses sequentially so as to record continuous frame segments in a frame of the film (refer to e.g. Japanese Patent 2524818).
Examples of the actual use of the motion detection imaging device such as described in the above-cited Japanese Laid-open Patent Publication 2003-32552 are monitor cameras such as rear monitor cameras for cars. In monitor cameras, it is desirable that the motion detection range is as wide as possible. For example, in the case of a room monitor camera placed on a wall of a room, it is desirable that the monitor camera can monitor a wide range (capture range or picture-taking range) over the entire area of the room in order to simplify the monitoring system and reduce the installation cost. However, in order for one room monitor camera to be able to image substantially the entire area of the room, it is normally required to use an optical lens having a view angle of at least 120° (degrees). Generally, an optical lens having a view angle much greater than 60°, as can be represented by a fisheye lens, causes a resultant image captured by the optical lens to have barrel distortion. This requires the use of complex programs to digitally correct the barrel distortion.
On the other hand, in order to monitor a range of at least 120° using a monitor camera with an optical lens having a view angle of at most 60°, it becomes necessary to use two or more of such monitor cameras, forming two or more capture ranges, and to adjust to prevent the capture ranges from forming a non-capture area therebetween. In other words, there has not been developed an imaging device for motion detection which is capable of capturing or imaging a wide range with a simple structure. In addition, in order to detect motion, it is necessary to prepare multiple images captured or imaged with a time difference. A conventional monitor camera or a similar device uses a shutter for imaging with a time difference, and opens and closes the shutter at predetermined intervals. However, in the case where the predetermined intervals of the shutter are long (frame rate is low), a problem arises that it is highly unlikely to detect motion of a target object moving at a high speed such as a moving car.